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Silicon substituted hydroxyapatite (SiHA) has been reported to produce faster bone in- growth in vitro compared to hydroxyapatite (HA). The mechanism by which silicate ions in these materials trigger bone growth and differentiation remains unclear. In vitro models were used in this thesis to investigate human osteoblast cell responses on exposure to silicon containing materials and silicate ion solutions. The amounts of serum protein bound to SiHA was significantly higher than that in HA (p<O.OOl). Culture of both primary human osteoblast (HOB) cells and an osteosarcoma cell line (MG-63 cells) showed that SiHA discs were biocompatible to the cells; flat cell morphologies, higher degree of cellular processes, and a covering with minuscule bone mineral-like crystals were observed. To elucidate the effects of silicate ions alone on osteoblast functions, a 1000 ppm standard silicon solution was supplemented into cell culture medium to produce silicate ion concentration of 20 and 500 ~M; it was found that the former had little effect on both cell types. Significant increases in levels of total DNA (p<0.001), protein (p<0.001), and collagen (p<0.001) were observed in HOB cells, but not in MG-63 cells, in cultures with 500 ~M silicate ions. Likewise, expression of COL-J al (p<0.001), BMP-2 (p<0.05), PHOSPHO-J (p<0.001) genes were up-regulated in both cells types cultured with 500 ~M silicate ions. Further studies proposed that the activation of cell proliferation by this silicate ion-containing medium, observed as increases in total DNA, involved TGF~1 and/or IGF-I receptors. In trying to understand this, it was latterly identified that the pH changes of the serum- supplemented culture medium that occurred during supplementation with the alkali silicate ion solution and subsequent neutralisation with HCI were the actual cause of the marked enhancement in HOB cell proliferation. Silicate ions did still appear to have a direct effect on some HOB cell responses, due to observing comparable effects of 20 and 500 ~M silicate ions on e.g. TNAP and PHOSPHO-J gene expression, compared to silicate ion-free controls.

by Wong Ho Man, Bruce. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves [60-61]). / Text in English; abstracts in English and Chinese. / by Wong Ho Man, Bruce. / Acknowledgements --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Table of Contents --- p.iv / List of figures --- p.vi / Chapter Chapter1 --- Introduction --- p.1 / Chapter Chapter 2 --- Fabrication of erbium-doped sol-gel derived silica --- p.4 / Chapter 2.1 --- Introduction to the sol-gel process --- p.4 / Chapter 2.1.1 --- The procedure for silica formation - ´ؤ --- p.7 / Chapter 2.1.2 --- Changes during the sol-gel process --- p.11 / Chapter 2.2 --- Factors affecting the fluorescence --- p.15 / Chapter 2.2.1 --- Clustering of Er3+ ions in the silica samples --- p.15 / Chapter 2.2.2 --- Retention of hydroxyl group OH/absorbed water in silica - --- p.16 / Chapter 2.3 --- The role of Aluminum in dissolving Er3+ ions in Si02 network --- p.18 / Chapter 2.4 --- Thermal dehydroxylation --- p.20 / Chapter 2.5 --- Characterization of the Erbium-doped silica samples --- p.24 / Chapter 2.5.1 --- Absorption spectrum --- p.24 / Chapter 2.5.2 --- "Refractive index, density and microhardness" --- p.29 / Chapter Chapter 3 --- Fluorescence spectroscopy --- p.35 / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Experimental set-up --- p.36 / Chapter 3.3 --- "Fluorescence spectrum with variation in Er3+ concentration, Al/Er molar ratio and annealing temperature" --- p.38 / Chapter Chapter 4 --- Decay lifetime measurements of the 4S3/2 energy level --- p.47 / Chapter 4.1 --- Introduction --- p.47 / Chapter 4.2 --- Experimental set-up --- p.48 / Chapter 4.3 --- Increase in decay lifetimes with Aluminum-codoping --- p.49 / Chapter Chapter 5 --- Conclusions and further works --- p.58 / References

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Thèse doctorat : Matériaux Polymères et Composites : Villeurbanne, INSA : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 207-221.

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